liveMedia/H264or5VideoStreamDiscreteFramer.cpp

/**********
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**********/
// "liveMedia"
// Copyright (c) 1996-2020 Live Networks, Inc.  All rights reserved.
// A simplified version of "H264or5VideoStreamFramer" that takes only complete,
// discrete frames (rather than an arbitrary byte stream) as input.
// This avoids the parsing and data copying overhead of the full
// "H264or5VideoStreamFramer".
// Implementation

#include "H264or5VideoStreamDiscreteFramer.hh"

H264or5VideoStreamDiscreteFramer
::H264or5VideoStreamDiscreteFramer(int hNumber, UsageEnvironment& env, FramedSource* inputSource,
				   Boolean includeStartCodeInOutput,
				   Boolean insertAccessUnitDelimiters)
  : H264or5VideoStreamFramer(hNumber, env, inputSource, False/*don't create a parser*/,
			     includeStartCodeInOutput, insertAccessUnitDelimiters) {
}

H264or5VideoStreamDiscreteFramer::~H264or5VideoStreamDiscreteFramer() {
}

void H264or5VideoStreamDiscreteFramer::doGetNextFrame() {
  if (fIncludeStartCodeInOutput) {
    // Prepend a 4-byte 'start code' (0x00000001) to the output:
    if (fMaxSize < 4) {  // there's no space
      fNumTruncatedBytes = 4 - fMaxSize;
      handleClosure();
      return;
    }
    *fTo++ = 0x00; *fTo++ = 0x00; *fTo++ = 0x00; *fTo++ = 0x01;
    fMaxSize -= 4;
  }

  if (fInsertAccessUnitDelimiters && pictureEndMarker()) {
    // Deliver an "access_unit_delimiter" NAL unit instead:
    unsigned const audNALSize = fHNumber == 264 ? 2 : 3;

    if (audNALSize > fMaxSize) { // there's no space
      fNumTruncatedBytes = audNALSize - fMaxSize;
      handleClosure();
      return;
    }

    if (fHNumber == 264) {
      *fTo++ = 9; // "Access unit delimiter" nal_unit_type
      *fTo++ = 0xF0; // "primary_pic_type" (7); "rbsp_trailing_bits()"
    } else { // H.265
      *fTo++ = 35<<1; // "Access unit delimiter" nal_unit_type
      *fTo++ = 0; // "nuh_layer_id" (0); "nuh_temporal_id_plus1" (0) (Is this correct??)
      *fTo++ = 0x50; // "pic_type" (2); "rbsp_trailing_bits()" (Is this correct??)
    }

    fFrameSize = (fIncludeStartCodeInOutput ? 4: 0) + audNALSize;
    pictureEndMarker() = False; // for next time
    afterGetting(this); // complete delivery to the downstream object
  } else {
    // Normal case:
    // Arrange to read data (which should be a complete H.264 or H.265 NAL unit)
    // from our data source, directly into the client's input buffer.
    // After reading this, we'll do some parsing on the frame.
    fInputSource->getNextFrame(fTo, fMaxSize,
			       afterGettingFrame, this,
			       FramedSource::handleClosure, this);
  }
}

void H264or5VideoStreamDiscreteFramer
::afterGettingFrame(void* clientData, unsigned frameSize,
                    unsigned numTruncatedBytes,
                    struct timeval presentationTime,
                    unsigned durationInMicroseconds) {
  H264or5VideoStreamDiscreteFramer* source = (H264or5VideoStreamDiscreteFramer*)clientData;
  source->afterGettingFrame1(frameSize, numTruncatedBytes, presentationTime, durationInMicroseconds);
}

void H264or5VideoStreamDiscreteFramer
::afterGettingFrame1(unsigned frameSize, unsigned numTruncatedBytes,
                     struct timeval presentationTime,
                     unsigned durationInMicroseconds) {
  // Get the "nal_unit_type", to see if this NAL unit is one that we want to save a copy of:
  u_int8_t nal_unit_type;
  if (fHNumber == 264 && frameSize >= 1) {
    nal_unit_type = fTo[0]&0x1F;
  } else if (fHNumber == 265 && frameSize >= 2) {
    nal_unit_type = (fTo[0]&0x7E)>>1;
  } else {
    // This is too short to be a valid NAL unit, so just assume a bogus nal_unit_type
    nal_unit_type = 0xFF;
  }

  // Begin by checking for a (likely) common error: NAL units that (erroneously) begin with a
  // 0x00000001 or 0x000001 'start code'.  (Those start codes should only be in byte-stream data;
  // *not* data that consists of discrete NAL units.)
  // Once again, to be clear: The NAL units that you feed to a "H264or5VideoStreamDiscreteFramer"
  // MUST NOT include start codes.
  if (frameSize >= 4 && fTo[0] == 0 && fTo[1] == 0 && ((fTo[2] == 0 && fTo[3] == 1) || fTo[2] == 1)) {
    envir() << "H264or5VideoStreamDiscreteFramer error: MPEG 'start code' seen in the input\n";
  } else if (isVPS(nal_unit_type)) { // Video parameter set (VPS)
    saveCopyOfVPS(fTo, frameSize);
  } else if (isSPS(nal_unit_type)) { // Sequence parameter set (SPS)
    saveCopyOfSPS(fTo, frameSize);
  } else if (isPPS(nal_unit_type)) { // Picture parameter set (PPS)
    saveCopyOfPPS(fTo, frameSize);
  }

  fPictureEndMarker = nalUnitEndsAccessUnit(nal_unit_type);

  // Finally, complete delivery to the client:
  fFrameSize = fIncludeStartCodeInOutput ? (4+frameSize) : frameSize;
  fNumTruncatedBytes = numTruncatedBytes;
  fPresentationTime = presentationTime;
  fDurationInMicroseconds = durationInMicroseconds;
  afterGetting(this);
}

Boolean H264or5VideoStreamDiscreteFramer::nalUnitEndsAccessUnit(u_int8_t nal_unit_type) {
  // Check whether this NAL unit ends the current 'access unit' (basically, a video frame).
  //  Unfortunately, we can't do this reliably, because we don't yet know anything about the
  // *next* NAL unit that we'll see.  So, we guess this as best as we can, by assuming that
  // if this NAL unit is a VCL NAL unit, then it ends the current 'access unit'.
  //
  // This will be wrong if you are streaming multiple 'slices' per picture.  In that case,
  // you can define a subclass that reimplements this virtual function to do the right thing.

  return isVCL(nal_unit_type);
}